Networks that primarily utilize data link layer devices are often referred to as layer two (L2) networks. A data link layer device is a device that operates within the second layer of the Open Systems Interconnection (OSI) reference model, i.e., the data link layer. One example of a common L2 networks is an Ethernet network in which end point devices (e.g., servers, printers, computers) are connected by one or more Ethernet switches or other L2 network devices. The Ethernet switches forward Ethernet frames, also referred to as L2 communications or L2 packets, to devices within the network. As the Ethernet switches forward the Ethernet frames the Ethernet switches learn L2 state information for the L2 network, including media access control (MAC) addressing information for the devices within the network and the physical ports through which the devices are reachable. The Ethernet switches typically store the MAC addressing information in MAC tables associated with each of their physical interfaces. When forwarding an individual Ethernet frame received on an ingress port of an Ethernet switch, the Ethernet switch typically multicasts the Ethernet frame to all of the other physical ports of the switch, unless the Ethernet switch has learned the specific physical port through which the destination MAC address devices is reachable. In this case, the Ethernet switch forwards a single copy of the Ethernet frame out the associated physical port.
Service provider networks provide layer 2 virtual private networking (L2VPN) services to connect customer networks over a wide area network. Example L2VPN services include Layer 2 circuits and Virtual Private Local Area Network (LAN) Service (VPLS).